JP5305982B2 - Energization control device and image forming apparatus - Google Patents

Abstract

Heating means (16) heated upon receiving power supplied from an AC power supply, temperature detecting means (312) detecting the temperature of the heating means (16), a memory (414) storing power energization pattern in which power energization and non-power energization are performed for each percentage of AC power, and power control means (411) that determines the percentage of AC power applied to the heating means (16) based on the temperature and that determines the power energization pattern by referring to the memory are provided. When the power energization percentage is changed, the power control means (411) changes the power energization pattern after the power energization percentage is changed in accordance with the changed power energization percentage based on the power energization pattern before the power energization percentage is changed and the power energization pattern after the power energization percentage is changed.

Description

  The present invention relates to an energization control apparatus that controls energization to a heater, and more particularly to an image forming apparatus that controls energization to a fixing unit used in an electrophotographic process.

  In an electrophotographic copying machine, a heat roller method is widely used as a method for fixing an image on a recording material such as paper. FIG. 2 is a cross-sectional view showing a fixing device using a heat roller system. On one surface of the recording paper P, a toner image formed on the photoreceptor is transferred. This toner image is fixed to the recording paper P by being heated and pressurized when the recording paper P passes between the fixing roll 202 and the pressure roll 203 along the direction of arrow A. The fixing roll 202 includes a cylindrical roll 202a and a halogen heater 202b as a heat source disposed in the cylindrical roll 202a. The heat roller system generally performs a stable fixing operation by increasing the heat capacity of the fixing roller and storing heat in the fixing roller. However, since the heat capacity is large, it takes a long time for the temperature of the fixing roller to reach a desired temperature. Further, there is a problem that power is consumed to keep the temperature of the fixing roller constant even during the standby of the image forming operation.

  As a technique for shortening this waiting time, a film heating type heating apparatus as in Patent Document 1 is used. In a film heating type fixing device, a planar heater such as a ceramic heater (hereinafter referred to as a planar heater) is used as a heat source.

  Since the fixing device using the ceramic heater as described above performs the fixing operation by directly pressing the film sliding on the heater against the recording paper, the temperature of the heater greatly affects the fixing temperature of the recording material. For this reason, in order to reduce the temperature ripple of the heater, it is necessary to stabilize the heater temperature in fine time units. As a fine time unit control method, a method of controlling the energization ratio to the heater per unit time is generally employed. As a control method for controlling the energization ratio, a technique is used in which the energization ratio for, for example, 20 half waves (200 ms) is adjusted using one half wave of the AC voltage (50 Hz) of the commercial power supply as a unit time. In this adjustment method, an energization pattern table in which the energization ratio is changed in increments of 10% when the energization state of all 20 half waves is 100% is used. Further, in order to keep the fixing temperature constant, a required energization amount is calculated by comparing the detection result of the heater temperature with the target fixing temperature every 200 ms, and the energization pattern in the next 200 ms is determined.

  However, the occurrence of flicker sometimes becomes a problem by changing the energization amount to the heater at a relatively high speed. Flicker is a state in which lighting connected to the same power supply line flickers due to power supply voltage fluctuation caused by power consumption in the appliance.

  Patent Documents 2 and 3 disclose solutions to such a film heating type flicker using a resistor heater. According to Patent Document 2, the amount of power supply voltage drop according to the type of energization pattern is obtained by equalizing the energization amount per unit time for the two resistor heaters and giving a difference in resistance value between the two heaters. The difference is reduced. According to Patent Document 3, a heater control pattern is assigned to each heater temperature range, and the power supply voltage fluctuation is suppressed by sequentially switching the pattern.

JP-A-63-313182 JP 2006-72235 A JP 2002-50450 A

  The amount of flicker generated is regulated based on IEC standards in the EC market (Europe). According to the IEC61000-3-3 standard, flicker is measured using a flicker meter, and the value is expressed as a Pst value, and Pst = 1.00 or less. Furthermore, the Pst value is calculated from the power supply voltage fluctuation amount and flicker meter response characteristics centered on 8.8 Hz. The response characteristic at this time corresponds to the human flicker perception threshold standard, that is, the closer to 8.8 Hz, the more easily humans perceive flicker.

  In the heating device used in the image forming apparatus, the power consumption is relatively large at about 1000 W, and flicker is easily generated because the energization amount is periodically changed for temperature control of the fixing heater.

  The power supply to the heating device is usually performed from a commercial power source that is an AC power source. At this time, in order not to adversely affect the power source, it is necessary to make the energization ratios of the positive side and the negative side equal (positive / negative symmetrical) in unit time (full wave in the AC power source). In order to keep the fixing temperature within a certain temperature range, an energization pattern is selected every certain unit time. Further, in order to keep positive and negative targets, the energization pattern is one in which the energization / non-energization state of the heater is switched with a positive half wave and a negative half wave as a set. From this, the heater energization frequency is distributed to a low order and a high order centering around 50 Hz which is a commercial power supply frequency. Furthermore, since the heater energization pattern switching is performed at a timing using a plurality of half waves of the commercial power supply, it is performed at a frequency lower than 50 Hz. In Patent Documents 2 and 3, it has not been considered that flicker sensitivity is increased by switching the energization pattern at such a low frequency.

In order to solve the above-described problems, an energization control device of the present invention includes a heating unit that is heated by receiving power supply from an AC power source, a temperature detection unit that detects the temperature of the heating unit, and the heating unit. A memory storing energization patterns representing energization and non-energization patterns for each AC energization ratio to be supplied, and an AC energization ratio from the AC power source to the heating means based on the temperature detected by the temperature detection means Power control means for determining an energization pattern to the heating means with reference to the memory, and the power control means, when changing the energization ratio, the energization pattern before the change of the energization ratio If the energization or non-energization continues for a predetermined period in the connected energization pattern in which the energization pattern after the change of the energization ratio is connected to the energization pattern, And changes the energization pattern after the change of the power energization percentage so that a predetermined period not continuous.

An image forming apparatus according to the present invention is an image forming apparatus using the above-described energization control device, and fixes an image forming unit that forms a toner image on a sheet and the toner image formed on the sheet to the sheet . characterized in that it have a fixing unit provided with the heating means to be heated by receiving electric power supplied from the AC power supply in order.

  According to the present invention, it is possible to suppress the occurrence of flicker when the energization ratio to the heating device is changed.

FIG. 3 is a cross-sectional view illustrating a configuration of an image forming apparatus. FIG. 3 is a diagram illustrating an example of a fixing device. FIG. 3 is a diagram illustrating an example of a fixing device. The block diagram which shows a heater control part. The figure which shows the electricity supply table to a heater. The figure which shows the electricity supply waveform to a heater. The figure which shows the electricity supply waveform to a heater. The flowchart which shows the switching determination process of an electricity supply pattern. The figure which produced | generated the control pattern from the electricity supply ratio. The figure which shows the electricity supply table to a heater. The figure which shows the frequency component of on / off switching of a heater. The figure which shows the weighted integration value with respect to frequency distribution.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an electrophotographic color image forming apparatus to which the present invention is applied. The image forming apparatus includes an image forming unit 1Y that forms a yellow image, an image forming unit 1M that forms a magenta image, an image forming unit 1C that forms a cyan image, and an image that forms a black image. Four image forming units (image forming units) of the forming unit 1Bk are provided. These four image forming units 1Y, 1M, 1C, and 1Bk are arranged in a line at regular intervals. The image forming apparatus includes sheet feeding units 17 and 20 for feeding recording sheets below the image forming unit, and further includes a fixing unit 16 above the image forming unit.

  Next, each unit will be described in detail. In each of the image forming units 1Y, 1M, 1C, and 1Bk, drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 2a, 2b, 2c, and 2d are installed as image carriers. Around each photosensitive drum 2a, 2b, 2c, 2d, there are primary chargers 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d as transfer means, Drum cleaner devices 6a, 6b, 6c and 6d are respectively arranged. A laser exposure device 7 is installed below the primary chargers 3a, 3b, 3c, 3d and the developing devices 4a, 4b, 4c, 4d. Each of the photosensitive drums 2a, 2b, 2c, and 2d is a negatively charged OPC photosensitive member having a photoconductive layer on an aluminum drum base, and is driven in an arrow direction (clockwise direction) by a driving device (not shown). It is rotationally driven at a predetermined process speed. Primary chargers 3a, 3b, 3c, and 3d as primary charging means bring the surface of each photosensitive drum 2a, 2b, 2c, and 2d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown). Charge uniformly. The laser exposure device 7 includes a laser light emitting element that emits light corresponding to a time-series electric digital pixel signal of image information to be given, a polygon lens, a reflection mirror, and the like, and exposes each of the photosensitive drums 2a to 2d. By this exposure, electrostatic latent images of respective colors corresponding to the image information are formed on the surfaces of the photosensitive drums 2a to 2d charged by the primary chargers 3a to 3d. The detailed configuration of the laser exposure apparatus 7 will be described later. Each of the developing devices 4a to 4d contains yellow toner, cyan toner, magenta toner, and black toner, and attaches each color toner to each electrostatic latent image formed on each photosensitive drum 2a to 2d. Development (visualization) as a toner image. The transfer rollers 5a to 5d as primary transfer means are arranged so as to be in contact with the respective photosensitive drums 2a to 2d via the intermediate transfer belt 8 in the respective primary transfer portions 32a to 32d. The toner images are sequentially transferred onto the intermediate transfer belt 8 and superimposed. The drum cleaners 6a to 6d are composed of a cleaning blade or the like, and scrape off the transfer residual toner remaining on the photosensitive drums 2a to 2d during the primary transfer from the photosensitive drums 2a to 2d to clean the surfaces of the drums. The intermediate transfer belt 8 is disposed on the upper surface side of each of the photosensitive drums 2 a to 2 d and is stretched between the secondary transfer counter roller 10 and the tension roller 11. The secondary transfer counter roller 10 is disposed in the secondary transfer portion 34 so as to be in contact with the secondary transfer roller 12 via the intermediate transfer belt 8. The intermediate transfer belt 8 is made of a dielectric resin such as a polycarbonate, a polyethylene terephthalate resin film, a polyvinylidene fluoride resin film, or the like. The image transferred to the intermediate transfer belt 8 is conveyed from the paper supply unit 17 and transferred to the recording sheet in the secondary transfer unit 34. Outside the intermediate transfer belt 8 and in the vicinity of the tension roller 11, a belt cleaning device 13 for removing and collecting the transfer residual toner remaining on the surface of the intermediate transfer belt 8 is installed. Image formation with each toner is performed by the process described above.

  The paper feeding unit includes a cassette 17 for storing recording sheets P and a manual feed tray 20. Further, a pickup roller (not shown) for feeding the recording sheets P one by one from the cassette or the manual feed tray, and a paper feeding roller for transporting the recording sheets P sent from the respective pickup rollers to the registration roller 19 are provided. It has been. The registration roller 19 temporarily stops the fed sheet, and sends the recording sheet P to the secondary transfer roller 12 in accordance with the image forming timing of the image forming unit.

  The fixing unit 16 includes a fixing film 16a provided with a heat source such as an alumina heater and a pressure roller 16b (which may be provided with a heat source in some cases) pressed against the substrate with the film interposed therebetween. The fixing unit functions as a heating unit that is heated by receiving power from an AC power source. Further, on the downstream side of the fixing unit 16, an outer paper discharge roller 21 for guiding the recording sheet P discharged from the fixing unit 16 to the outside of the apparatus is disposed.

  Next, the configuration of a film heating type fixing device (hereinafter referred to as a fixing device) used in this embodiment will be described.

  FIG. 3 is a configuration diagram showing details of the fixing device 16. 301 is a ceramic heater, 302 is a fixing film, 303 is a pressure roller, 311 is a sheet metal, 312 is a thermistor for detecting the temperature of the heater, 313 is a holder for attaching the thermistor 312 and the heater 301, and 314 is a self-bias circuit. . The fixing film 302 corresponds to the fixing film 16a in FIG. 1, and the pressure roller 303 corresponds to the pressure roller 16b in FIG. The heater 301 is a heater (see FIG. 8) in which a heat generation pattern is printed on ceramic, and is a highly responsive heater that rises in temperature by about 50 ° C. per second. The fixing film 302 is made of a metal base, a rubber layer having a thickness of about 300 μm, and a fluorine surface treatment. The fixing film 302 has a very small heat capacity and transmits heat from the heater only to the nip portion. The pressure roller 303 is a roller having a hardness of about 60 ° and frictionally drives the fixing film 302. The sheet metal 311 presses the fixing film 302 against the pressure roller 303 from the inside, and the pressure is about 180N. The thermistor 312 has a main thermistor disposed at the center of the heater and a sub thermistor disposed at the heater end. The sub-thermistor detects a temperature rise in the non-sheet passing portion of the fixing device 16 when a small size paper such as B5 size is passed.

  The toner image on the recording paper P is heated and pressurized (pressed by a surface heater and a pressure roller) when the recording paper P passes between the film 302 and the pressure roller 303 along the direction of the arrow. As a result, the recording paper P is fixed. Although the heater 301 is fixed, the film 302 is configured to rotate as the pressure roller rotates. In the fixing method according to this configuration, the heat of the heater 301 is immediately transmitted to the recording paper P through the film, so that the time from the start of heating to the planar heater until printing becomes possible is short.

  Next, a circuit for controlling energization of the heater 301 in the fixing device 16 will be described.

  FIG. 4 is a circuit diagram illustrating a configuration of a control circuit that performs drive control and failure detection of the heater 301. In FIG. 1A, reference numeral 411 denotes a CPU for controlling the operation of this control circuit. Reference numerals 400-1 and 400-2 denote heater circuits each having the same structure. The heater 301 includes two heaters provided upstream and downstream along the conveyance direction of the recording paper P, and the drive circuits of the heaters correspond to the heater circuits 400-1 and 400-2. FIG. 5B is a circuit showing details of the heater circuits 400-1 and 400-2, and representatively shows only one heater circuit. Reference numeral 401 denotes an AC power source such as a commercial power source that supplies power to the entire printer. The heater 301 generates heat when power is supplied from the AC power supply 401. Reference numeral 404 denotes a triac for turning on / off the energization of the heater 301 from the AC power supply 401. Reference numerals 405 and 406 denote bias resistors for the triac 404. Reference numeral 407 denotes a phototriac coupler, which is connected in series between resistors 405 and 406. When the light-emitting diode of the phototriac coupler 407 is energized, the triac 404 is turned on. The phototriac coupler 407 also has a function as a device for ensuring a creepage distance between the primary side and the secondary side of the power source. Reference numeral 408 denotes a resistor for limiting the current of the phototriac coupler 407. Reference numeral 410 denotes a resistor, and reference numeral 409 denotes a transistor for controlling energization to the light emitting diode of the phototriac coupler 407, which is turned on by an ON signal from the CPU 411 to cause the light emitting diode to emit light.

  The temperature of the heater 301 is detected by the thermistor 312. The thermistor 312 has a characteristic (NTC characteristic) in which the resistance value decreases with increasing temperature. The power supply voltage Vcc is divided by the resistor 412 and the thermistor 312, and the CPU 411 detects the temperature of the heater 301 by detecting the divided voltage. The thermistor 312 functions as a detection unit that detects the temperature of the heater 301 that is a part of the heating unit.

  Next, a method for controlling the fixing device 16 will be described with reference to FIG.

  FIG. 5 is a diagram showing an energization table in the case where a heating device (fixing device) having two heaters is provided. This energization table is stored in the ROM 414. In order to control the energization ratio to each heater, energization / non-energization patterns of the respective heating elements, that is, energization patterns representing the order of energization and de-energization are defined in units of eight half waves. The energization control is performed by executing in order of the first half wave to the eighth half wave. The leftmost column in the figure represents the energization ratio (%), 0 in the third column and thereafter represents non-energization, and 1 represents energization. In the energization pattern, the energization ratio is determined in increments of 12.5%, and each energization pattern is determined for each of the upstream and downstream heaters. The first half wave and the second half wave are in the same state of energization and non-energization so that the current waveform to each heater is positive and negative and symmetric in all the waves of the AC commercial power supply. Similarly, the third half-wave and the fourth half-wave, the fifth half-wave and the sixth half-wave, and the seventh half-wave and the eighth half-wave are in the same state. That is, the nth half wave (n is a natural number) and the (n + 1) th half wave have the same energized and non-energized states, and the energies are different in polarity. The CPU 411 compares the temperature detected by the thermistor 312 with the target temperature, determines the energization ratio by well-known PID control with respect to the temperature change, and controls the energization to each heater according to the energization pattern corresponding to the determined energization ratio. . The ROM 414 functions as a memory that stores an energization pattern representing the order of energization and non-energization for each AC energization ratio. FIG. 6 is a waveform diagram showing a waveform of a current supplied to the heater. Reference numerals 601 and 602 denote current waveforms flowing through the respective heaters when control is performed based on the energization table shown in FIG. Reference numeral 603 represents the total amount of current used by both heaters. The current waveform to each heater is controlled to be positive and negative and symmetric in all the waves of the AC commercial power supply. The CPU 411 changes the energization ratio based on the temperature change detected by the thermistor 312, but the energization pattern change determination is performed at an energization pattern change determination point 605 for each cycle T (four half waves) shown in the figure. The timing for changing the energization ratio is performed at the energization ratio change point 604 shown in the figure. The CPU 411 controls the heater temperature to be the target temperature by changing the energization ratio stepwise, for example, 62.5% → 50% → 37.5%. Further, the CPU 411 determines whether or not to change the energization ratio at the energization ratio change timing for each period T based on the waveform of the commercial AC power supply. When the change is not performed, the energization according to the determined energization pattern is continued without changing the energization ratio, and when the change is made, the control is performed with the energization pattern based on the changed energization ratio. At this time, in order to satisfy the positive and negative targets in all the waves of the commercial AC power supply, the period T is 2 × n with a minimum unit of two half waves. In the present embodiment, the period T is four half waves. The CPU 411 functions as a power control unit that determines an AC energization ratio and determines an energization pattern for the heater 301 serving as a heating unit with reference to the ROM 414 serving as a memory.

  As a result of such switching of the energization ratio, a continuous non-energization state may occur before and after the energization ratio change point 604. FIG. 7 shows a waveform when the control is switched from 37.5% to 25% as an example. 701 represents the current flowing through the upstream heater, 702 represents the current flowing through the downstream heater, and 703 represents the total current. At this time, a continuous non-energized state for six half-waves occurs in the total current value of 703 at the switching timing of the energization ratio.

  On the other hand, if the energization pattern is such that the total current of the two heaters when the energization ratio is 25% is as indicated by 704, the number of times the heater is energized and de-energized increases, and the frequency of switching is higher Will shift to. In 703, when the energization ratio is switched from 37.5% to 25%, control of 6 half-waves on (energization) → 6 half-waves off (non-energization) → 4 half-waves on (energization) is performed. Then, the on / off frequency of energization has a frequency component of 8.3 Hz. This frequency is a value close to a frequency of 8.8 Hz where humans can easily feel flicker. On the other hand, if the energization pattern is rearranged as in 704, the on / off frequency of energization transitions to 10 Hz. Thus, flicker reduction is realized by the fact that the on / off frequency of energization transitions from the vicinity of 8.3 Hz where flicker sensitivity is high to 10 Hz. That is, the CPU 411 compares the energization pattern for a predetermined period before the change of the energization ratio with the energization pattern for the predetermined period after the change of the energization ratio, and determines the energization pattern determined corresponding to the changed energization ratio. Determine whether to change. Specifically, the energization pattern is changed so that the on / off frequency of energization increases when energization or non-energization continues for a predetermined period before and after the energization ratio is changed.

  A method for replacing the energization pattern will be specifically described. In the energization table of FIG. 5, for example, when pattern replacement is performed with a set of four half-waves, the energization pattern is replaced by comparing the next selected quarter-wave pattern with the previous quarter wave. It is determined whether or not to do so.

  The energization pattern replacement determination process will be described with reference to FIG. The flowchart in FIG. 8 is executed by the CPU 411 based on a program stored in the ROM 414.

  In order to determine the energization pattern of the next four half-waves after the energization pattern change point 604, the CPU 411 determines the four half-waves immediately before the change point 604 (referred to as the previous four-half waves) and the four half-waves immediately after the switching timing 604 (next). (Referred to as 4 half-waves). The first to fourth half waves of the front four half waves are referred to as the first first half wave to the previous fourth half wave, respectively, and the first to fourth half waves of the next four half wave are respectively the first half wave. ~ Called the fourth half wave. First, the CPU 411 compares the energization amounts of the previous fourth half wave immediately before the change point 604 and the next first half wave immediately after the change point 604 (step S901). As described above, since the nth half wave and the (n + 1) th half wave of the energization pattern have the same energization state and different polarities, the comparison of the charge amounts of the previous fourth half wave and the next first half wave is The energization amounts of the half wave / front fourth half wave and the next first half wave / next second half wave are compared. The comparison of the energization amount is performed with respect to the total current of the upstream and downstream heaters. If both heaters are not energized, the energization amount is 0. If one heater is energized, the energization amount is 1. If both heaters are energized, the energization amount is 2. At this time, if the energization amounts of the previous fourth half wave and the next first half wave are equal, the CPU 411 replaces the energization patterns. That is, the CPU 411 includes the first and second half waves (next first half wave and next second half wave) and the third and fourth half waves (next third half wave) immediately after the change point 604. A process of switching the energization pattern of the wave and the next fourth half wave is performed (S907). That is, the energization control is performed in the order of the third → fourth → first → second half wave of the pattern defined in the energization pattern table.

  When the energization amounts are not equal in step S901, the CPU 411 compares the energization amounts of the previous fourth half wave and the next fourth half wave (step S902). At this time, if the respective energization amounts are equal, the CPU 411 determines not to perform the energization pattern replacement process, and controls the heater 301 with the energization pattern as it is (step S908).

  Next, when the energization amounts are not equal in S902, the CPU 411 determines whether the energization amounts of the previous first half wave and the next fourth half wave are equal (S903). If the respective energization amounts are equal, the CPU 411 performs an energization pattern replacement process, and if not equal, proceeds to step S904.

  In step S904, the CPU 411 determines whether the energization amount of the previous first half wave is larger than the energization amount of the next fourth half wave. If the energization amount of the previous first half wave is larger than the energization amount of the next fourth half wave, the process proceeds to step S906, and if not, the process proceeds to step S905.

  In step S906, the CPU 411 determines whether the energization amount of the previous fourth half wave is larger than the energization amount of the next first half wave. When the energization amount of the previous fourth half wave is larger than the energization amount of the next first half wave, the CPU 411 changes the energization pattern. On the other hand, when the energization amount of the previous fourth half-wave is not larger than the energization amount of the next first half-wave, the CPU 411 controls the heater 301 with the energization pattern as it is without performing the energization pattern replacement process.

  In step S905, the CPU 411 determines whether the energization amount of the previous fourth half wave is smaller than the energization amount of the next first half wave. When the energization amount of the previous fourth half wave is smaller than the energization amount of the next first half wave, the CPU 411 changes the energization pattern. On the other hand, when the energization amount of the previous fourth half wave is not smaller than the energization amount of the next first half wave, the CPU 411 controls the heater 301 with the energization pattern as it is without replacing the energization pattern. Thus, comparing the energization amount in the energization pattern before the energization ratio change and the energization pattern after the change determines whether or not the frequency of switching between energization and non-energization is a predetermined value or less.

  In the example of FIG. 7, since the energization amount in the previous fourth half wave before the energization ratio change is 0 and the energization amount in the next first half wave after the energization ratio change is 0, Yes in step S901 and step S907. The energization pattern is exchanged at.

  With the above processing, the number of switching between energization / non-energization can be increased while maintaining the energization ratio, and the frequency component of the heater energization pattern is shifted to a higher frequency side.

  The replacement determination process may be performed not only when the energization ratio is changed but also every time the heater is driven for four half waves. That is, the four half waves (first to fourth half waves) after the energization ratio is changed and the next four half waves (fifth to eighth half waves) are compared, and the fifth to eighth waves are compared. The half wave and the first to fourth half waves of the next period are compared.

  As another method, a method using table switching will be described. FIG. 10 is a table obtained by reversing the control order. Specifically, the pattern of FIG. 5 is divided into four half waves, and the order of the first half wave, the second half wave, the third half wave, and the fourth half wave is changed for each of the four half waves. It is a pattern. Since it is divided every four half-waves, the energization patterns of the fifth half-wave, the sixth half-wave, the seventh half-wave, and the eighth half-wave in FIG. 5 are also switched. The CPU 411 calculates the number of changes in the amount of energization when the tables in FIGS. 5 and 10 are selected as the energization pattern change determination, and controls the flicker suppressed by selecting the table with the larger number of changes from the calculation result. Can be done.

  FIG. 9 is a diagram in which an energization table is generated from the energization ratio. FIG. 9 shows a case where the energization ratio is 50%. In order to set the energization ratio to 50%, the energization period is required for four half waves in the next period (901). It is divided into two half-waves so that the energization period for the four half-waves is not continuous (904). In this manner, even when the energization table is not provided, a pattern 902 that is discontinuous with the previous energization pattern and has a maximum frequency within the control cycle can be generated based on the energization ratio.

  The energization pattern switching determination may be performed at an arbitrary period T.

  Alternatively, a method of selecting an energization pattern that minimizes the flicker component using the frequency component of the energization pattern may be used. FIG. 11 is a diagram showing the relationship between the frequency distribution due to energization and the flicker threshold. When the energization / non-energization switching operation of the heater is performed by the fixing operation, a frequency distribution of the heater frequency component 1101 exists up to the vicinity of 50 Hz that is the frequency of the commercial power supply.

  Furthermore, as shown by the flicker threshold of 1102, flicker is the most human sensitive at 8.8 Hz. From these facts, it is possible to select the optimum energization pattern by measuring the frequency component generated by the energization pattern of the next period and evaluating the energization pattern from the flicker threshold.

  FIG. 12 shows weighting for each frequency around 8.8 Hz. The measured frequency distribution is weighted with respect to the frequency in the range of 0.5 Hz to 25 Hz, where 8.8 Hz shown in FIG. 12 is 1, and applied to each frequency, and each energization pattern is applied by weighted average. The evaluation value for the case is calculated. By applying the pattern having the lowest evaluation value, an energization pattern with less flicker can be obtained. As the method for determining the energization ratio and the energization pattern, the method described in the above embodiment can be used.

16 Fixing Device 301 Fixing Heater 401 AC Power Supply 411 CPU
414 ROM

Claims (5)

Heating means that is heated by receiving power supply from an AC power source;
Temperature detecting means for detecting the temperature of the heating means;
A memory that stores energization patterns representing energization and non-energization patterns for each AC energization ratio supplied to the heating means;
A power control unit that determines an AC energization ratio from the AC power source to the heating unit based on the temperature detected by the temperature detection unit, and that determines an energization pattern to the heating unit with reference to the memory ; have,
Before SL power control means, when changing the power energization percentage, if energized or de-energized in the consolidated energization pattern obtained by connecting the energization pattern after the change of the current ratio energization pattern before the change of the power energization percentage is continuous predetermined period An energization control apparatus that changes the energization pattern after changing the energization ratio so that energization or non-energization in the connected energization pattern does not continue for a predetermined period . The power control unit, 2 a half-wave × n AC (n is a natural number) electrification control apparatus according to claim 1, wherein the TURMERIC line changes energizing patterns for each period of the. The power control means, in the energizing pattern after changing the power energization percentage, claim 1, wherein the replacing timing to initially energizing said heating means, and a timing of the first non-energized said heating means energization control apparatus according to. The memory stores another energization pattern representing another pattern in which the timing at which the heating unit in the energization pattern is first energized and the timing at which the heating unit is first de-energized in the energization pattern are interchanged. And
If the energization or non-energization in the connection energization pattern continues for a predetermined period, the power control means refers to the memory and changes the energization pattern after changing the energization ratio to another energization pattern corresponding to the energization ratio. The energization control device according to claim 1, wherein: An image forming apparatus using the energization control device according to any one of claims 1 to 4 ,
Image forming means for forming a toner image on a sheet;
Fixing means comprising the heating means heated by receiving power supplied from an AC power source in order to fix the toner image formed on the sheet to the sheet;
An image forming apparatus characterized by have a.